Fuel management system comprising a fluoroelastomer layer having a hydrotalcite compound

ABSTRACT

A component of a fuel management system having a surface that in use will come into contact with fuel. The surface includes a fluoroelastomer layer. The fluoroelastomer layer comprises a hydrotalcite compound dispersed therein.

1. FIELD OF THE INVENTION

[0001] The present invention relates to a component of a fuel managementsystem comprising a fluoroelastomer layer, i.e. a layer of curedfluoropolymer having a fluorinated backbone, and a hydrotalcite compounddispersed therein. In particular, the present invention relates to theuse of a hydrotalcite compound to improve the resistance of thefluoroelastomer layer when brought in contact with diesel fuel, more inparticular with diesel fuel of biological origin.

2. BACKGROUND OF THE INVENTION

[0002] The beneficial properties of fluoroelastomers are well known inthe art and include for example, high temperature resistance, highchemical resistance including for example high resistance to solvents,fuels and corrosive chemicals and non-flammability. Because of thesebeneficial properties, fluoroelastomers find wide applicationparticularly where materials are exposed to high temperature and/orchemicals.

[0003] For example, fluoroelastomers are used in fuel management systemswhich include for example fuel storage components, such as a fuel tank,fuel pump couplers, filler neckhoses, fuel tank cap seal and the like;fuel delivery components, such as fuel line hoses and tubings, fuelfiller lines, fuel supply lines and in particular high temperature fuellines in cars or other motor vehicles because of their excellentresistance to fuels and because of the good barrier properties that canbe achieved with fluoroelastomers.

[0004] The fluoropolymers, which upon curing yield the fluoroelastomersare generally more expensive than non-fluorine polymers and accordingly,materials have been developed in which the fluoropolymer is used incombination with other materials to reduce the overall cost. Forexample, it has been proposed to use a relatively thin layer offluoroelastomer as an inner layer of a multilayer hose where theouterlayer of the hose is then a non-fluorine elastomer. For exampleU.S. Pat. No. 6,106,914 relates to a hose, having a laminate structure,comprising of a first layer formed of a fluoro rubber or a fluoro resinand as second layer formed of an epichlorohydrin. U.S. Pat. No.6,340,511 relates to a fuel hose comprising an inner layer offluoroelastomer and an outer layer formed from a blend of polyvinylchloride (PVC) and acrylonitrile butadiene rubber (NBR) that are adheredwell by vulcanisation.

[0005] In recent years, increased environmental concerns have led to thedevelopment of low emission diesel fuel, i.e. diesel fuel of biologicalorigin, comprising vegetable oil methyl ester. At severe conditions,i.e. high temperature and humidity, hydrolysis products can be formedthat will accelerate swelling and deterioration of the currently usedfuel management systems. A need exists for a fuel management systemhaving improved barrier properties. Accordingly, it would be desirableto find a way of improving the resistance of a fluoroelastomer layer,used in fuel management systems, when brought in contact with dieselfuel, more in particular with diesel fuel of biological origin.

3. SUMMARY OF THE INVENTION

[0006] In one embodiment, the present invention provides a component ofa fuel management system having a surface that in use will come intocontact with fuel, said surface comprising a fluoroelastomer layer. Thefluoroelastomer layer comprises a hydrotalcite compound dispersedtherein.

[0007] In a further aspect, the present invention relates to the use ofa hydrotalcite compound in the fluoroelastomer layer of a fuelmanagement component to prevent or reduce swelling of thefluoroelastomer layer when said fluoroelastomer layer is brought incontact with fuel, more in particular with diesel fuel of biologicalorigin.

[0008] Still in a further aspect, the present invention provides amethod of making a component of a fuel management system comprising thesteps of

[0009] providing a curable fluoroelastomer composition comprising afluoropolymer having one or more halogens capable of participating in acure reaction, an organic peroxide and a hydrotalcite compound; and

[0010] curing and shaping said curable fluoroelastomer composition toform a fluoroelastomer layer that in use will be in contact with fuel.

[0011] By the tern ‘fuel’ in connection with this invention is meantfuel used to drive a combustion engine in particular a diesel engine.The term fuel in connection with this invention includes in particularfuel or fuel mixtures comprising diesel of biological origin. By theterm ‘fuel management system’ is meant the total of components as usedin storing, supplying, metering and control of fuel emission and thatare exposed to or come in contact with fuel. Fuel management systemsinclude components comprised in a motor vehicle as well as components ofsystems exterior to a motor vehicle. Without limitation, components of afuel management system include fuel storage components such as fueltanks, filler neck hoses and fuel tank cap seals, fuel supply componentssuch as fuel line hoses or tubings used in a motor vehicle, fuel fillerhose for filling fuel to a fuel tank of a motor vehicle, valves,diaphragms and fuel injector components, fuel connector components suchas quick connect O-rings, emission control components such as emissioncontrol seals, air intake manifold gaskets and solenoid armatures.

4. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The following figures are included by way of further illustrationof some embodiments of the present invention. It will be understood thatthese drawings merely serve to illustrate the invention without limitingthe invention in any way thereto.

[0013]FIGS. 1 and 2 are cross-sectional schematic representations ofmulti-layer hoses or tubes that can be obtained with the invention.

5. DETAILED DESCRIPTION OF THE INVENTION

[0014] The hydrotalcite compound used in the present invention maycomprise a natural or synthetic hydrotalcite compound or mixturethereof. Particularly suitable hydrotalcite compounds are Mg and/or Alhydrocarbonate minerals of synthetic or natural origin. Examples ofnatural compounds include Hydrotalcite Mg₆Al₂(OH)₁₆CO₃.4H₂O and membersof the hydrotalcite group, such as; Stichtite Mg₆Cr₂(OH)₁₆CO₃.4H₂O;Pyroaurite Mg₆Fe(III)₂(OH)₁₆CO₃.4H₂O; DesautelsiteMg₆Mn(III)₂(OH)₆CO₃.4H₂O and the like.

[0015] The hydrotalcite compound may also be of a synthetic hydrotalcitecompound. Examples of synthetic hydrotalcite compounds include:Mg₆Al₂(OH)₁₆CO₃.4H₂O, Mg_(4.5)Al₂(OH)₁₃CO₃.3.5H₂O, Mg_(4.5)Al₂(OH)₁₃CO₃,Mg₄Al₂(OH)₁₂CO₃.3.5H₂O, Mg₅Al₂(OH)₁₄CO₃.4H₂O, Mg₃Al₂(OH)₁₀CO₃.1.7H₂O,Mg3ZnAl₂(OH)₁₂CO₃.wH₂O and Mg₃ZnAl₂(OH)₁₂CO₃. Synthetic hydrotalcitesthat are commercially available, include for example those availablefrom Kisuma Chemicals BV under the name DHT-4A™ and DHT-4V™ and ZHT-4A™;and Hycite™ 713 which is available from Ciba Specialties Chemicals.

[0016] Hydrotalcite compounds that can be used in connection with thepresent invention include in particular those that can be represented bythe formula:

[(M₁ ²⁺)_(a)(M₂ ²⁺)_(b)](M³⁺)_(y)(OH)_(2x+3y−2)(A^(n−))_(y/n)wH₂O

[0017] wherein M₁ ²⁺ represents at least one divalent metal selectedfrom the group consisting of Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺; M₂ ²⁺ representsat least one divalent metal selected from the group consisting of Zn²⁺,Cd²⁺, Pb²⁺ and Sn²⁺; M³⁺ represents a trivalent metal ion; A^(n−)represents an n− valent anion, such as F⁻, Cl⁻, Br⁻, NO₃ ⁻, CO₃ ²⁻, SO₄²⁻, Fe(CN)₆ ⁴⁻, CH₃COO⁻, oxalic acid ion or salicylic acid ion; a and brespectively represent a value from 0 to 10, x represents a+b and has avalue from 1 to 10, y represents an integer from 1 to 5, and wrepresents a real number. The hydrotalcite compound is typically used inthe fluoroelastomer layer in an amount between 0.3 and 20% by weightrelative to the amount of fluoroelastomer and preferably between 0.5 and10% by weight.

[0018] The fluoroelastomer layer comprises a fluoropolymer having apartially or fully fluorinated backbone. Particularly preferredfluoropolymers are those that have a backbone that is at least 30% byweight fluorinated, preferably at least 50% by weight fluorinated, morepreferably at least 65% by weight fluorinated. Examples offluoropolymers for use in this invention include polymers of one or morefluorinated monomers optionally in combination with one or morenon-fluorinated monomers. Examples of fluorinated monomers includefluorinated C₂-C₈ olefins that may have hydrogen and/or chlorine atomssuch as tetrafluoroethylene (TFE), chlorotrifluoroethylene (CTFE),2-chloropentafluoropropene, dichlorodifluoroethylene, vinyl fluoride,vinylidene fluoride (VDF) and fluorinated alkyl vinyl monomers such ashexafluoropropylene (HFP); fluorinated vinyl ethers, includingperfluorinated vinyl ethers (PVE) and fluorinated allyl ethers includingperfluorinated allyl ethers. Suitable non-fluorinated comonomers includevinyl chloride, vinylidene chloride and C₂-C₈ olefins such as ethylene(E) and propylene (P).

[0019] Examples of perfluorovinyl ethers that can be used in theinvention include those that correspond to the formula:

CF₂═CF—O—R_(f)

[0020] wherein R_(f) represents a perfluorinated aliphatic group thatmay contain one or more oxygen atoms.

[0021] Particularly preferred perfluorinated vinyl ethers correspond tothe formula:

CF₂=CFO(R^(a) _(f)O)_(n)(R^(b) _(f)O)_(m)R^(c) _(f)

[0022] wherein R^(a) _(f) and R^(b) _(f) are different linear orbranched perfluoroalkylene groups of 1-6 carbon atoms, in particular 2to 6 carbon atoms, m and n are independently 0-10 and R^(c) _(f) is aperfluoroalkyl group of 1-6 carbon atoms. Specific examples ofperfluorinated vinyl ethers include perfluoro (methyl vinyl) ether(PMVE), perfluoro (ethyl vinyl) ether (PEVE), perfluoro (n-propyl vinyl)ether (PPVE-1), perfluoro-2-propoxypropylvinyl ether (PPVE-2),perfluoro-3-methoxy-n-propylvinyl ether, perfluoro-2-methoxy-ethylvinylether and CF₃—(CF₂)₂—O—CF(CF₃)—CF₂—O—CF(CF₃)—CF₂—O—CF═CF₂.

[0023] Suitable perfluoroalkyl vinyl monomers correspond to the generalformula:

CF₂═CF—R^(d) _(f) or CH₂═CH—R^(d) _(f)

[0024] wherein R^(d) _(f) represents a perfluoroalkyl group of 1 to 10,preferably 1 to 5 carbon atoms. A typical example of a perfluoroalkylvinyl monomer is hexafluoropropylene.

[0025] The fluoropolymers for use in connection with the presentinvention can be made in accordance with any of the known polymerizationmethods for making fluoropolymers. Such methods include withoutlimitation, aqueous emulsion polymerization, suspension polymerizationand polymerization in an organic solvent.

[0026] The fluoropolymer for use in connection with the presentinvention is a substantially amorphous polymer that shows hardly anymelting point if at all. Such fluoropolymers are particularly suitablefor providing fluoroelastomers, which are typically obtained upon curingof an amorphous fluoropolymer. Amorphous fluoropolymers include forexample copolymers of vinylidene fluoride and at least one terminallyethylenically-unsaturated fluoromonomer containing at least one fluorineatom substituent on each double-bonded carbon atom, each carbon atom ofsaid fluoromonomer being substituted only with fluorine and optionallywith chlorine, hydrogen, a lower fluoroalkyl radical, or a lowerfluoroallkoxy radical. Specific examples of copolymers include forexample copolymers having a combination of monomers as follows: VDF-HFP,TFE-P, VDF-TFE-HFP, VDF-TFE-PVE, TFE-PVE, E-TFE-PVE and any of theaforementioned copolymers further including units derived from achlorine containing monomer such as CTFE. Still further examples ofsuitable amorphous copolymers include copolymers having a combination ofmonomers as in CTFE-P.

[0027] Preferred amorphous fluoropolymers generally comprise from 20 to85%, preferably 50 to 80% by moles of repeating units derived from VDF,TFE and/or CTFE, copolymerized with one or more other fluorinatedethylenically unsaturated monomer and/or one or more non fluorinatedC₂-C₈ olefins, such as ethylene and propylene. The units derived fromthe fluorinated ethylenically unsaturated comonomer when present isgenerally between 5 and 45 mole %, preferably between 10 and 35 mole %.The amount of non-fluorinated comonomer when present is generallybetween 0 and 50 mole %, preferably between 1 and 30 mole %.

[0028] The fluoropolymer will typically be cured. The fluoropolymerlayer may be cured by any of the methods known to those skilled in theart and will typically include a cure composition such that thefluoropolymer layer can be cured. The cure composition typicallyincludes one or more components that cause the fluoropolymer chains tolink with each other thereby forming a three dimensional network. Suchcomponents may include catalysts, curing agents and/or coagents.

[0029] In a preferred embodiment of curing the fluoropolymer layer a socalled peroxide cure system may be used. In a typical peroxide curesystem, the fluoropolymer is provided with one or more cure sites thatcomprise a halogen capable of participating in a peroxide cure reactionand the composition for providing the fluoropolymer contains an organicperoxide. The halogen capable of participating in a peroxide curereaction is typically bromine or iodine and may be distributed along thepolymer chain and/or may be contained in the end groups of thefluoropolymer. Typically, the amount of bromine or iodine contained inthe fluoropolymer is between 0.001 and 5%, preferably between 0.01 and2.5%, by weight with respect to the total weight of the fluoropolymer.It has further been found that also chlorine is capable of participatingin a peroxide cure reaction of the fluoropolymer if an organic compoundcomprising a hydride function MH, where M is selected from Si, Ge, Sn orPb, is present. Accordingly, also fluoropolymers that contain chlorineatoms and/or bromine or iodine can be used for curing in a peroxide curereaction. The amount of chlorine in the fluoropolymer may vary from0.001% by weight to 10% by weight but is typically between 0.01% byweight and 5% by weight based on the weight of fluoropolymer. Thefluoropolymer for use in the peroxide cure reaction typically will havea molecular weight of 10⁴ to 5×10⁵ g/mol and the molecular weightdistribution can be monomodal as well as bimodal or multimodal.

[0030] In order to introduce halogens, which are capable ofparticipation in the peroxide cure reaction, along the chain, thecopolymerization of the basic monomers of the fluoropolymer can becarried out with a suitable fluorinated cure-site monomer (see forinstance U.S. Pat. Nos. 4,745,165, 4,831,085, and 4,214,060). Suchcomonomer can be selected for instance from:

[0031] (a) bromo- or iodo- (per)fluoroalkyl-(per)fluorovinylethershaving the formula:

Z.R_(f)—O—CX═CX₂

[0032] wherein each X may be the same or different and represents H orF, Z is Br or I, R_(f) is a (per)fluoroalkylene C₁-C₁₂, optionallycontaining chlorine and/or ether oxygen atoms; for example:BrCF₂—O—CF═CF₂, BrCF₂CF₂—O—CF═CF₂, BrCF₂CF₂CF₂—O—CF═CF₂,CF₃CFBrCF₂—O—CF═CF₂, and the like; and

[0033] (b) bromo- or iodo perfluoroolefins such as those having theformula:

Z′-(R_(f)′)_(r)—CX═CX₂ and

[0034] wherein each X independently represents H or F, Z′ is Br or I,R′_(f) is a perfluoroalkylene C₁-C₁₂, optionally containing chlorineatoms and r is 0 or 1; for instance: bromotrifluoroethylene,4-bromo-perfluorobutene-1, and the like; or bromofluoroolefins such as1-bromo-2,2-difluoroethylene and 4-bromo-3,3,4,4-tetrafluorobutene-1;

[0035] (c) non-fluorinated bromo-olefins such as vinyl bromide and4-bromo-1-butene; and

[0036] (d) chlorine containing monomers including chlorine containingfluorinated monomers such as for example chlorine containing fluorinatedC₂-C₈ olefins such as CTFE and non-fluorinated chlorine containingmonomers such as chlorinated C₂-C₈ olefins such as vinyl chloride andvinylidene chloride.

[0037] In replacement of or in addition to the cure site comonomer, thefluoropolymer can contain a cure site component in terminal position,deriving from a suitable chain transfer agent introduced in the reactionmedium during the polymer preparation, as described in U.S. Pat. No.4,501,869 or derived from a suitable initiator. Examples of usefulinitiators include X(CF₂)_(n)SO₂Na with n=1 to 10 (where X is Br or I).Still further, the initiation and/or polymerization may be conducted inthe presence of a halide salt such as a metal or ammonium halideincluding for example potassium chloride, sodium chloride, potassiumbromide, aminonium bromide or chloride and potassium or sodium iodide tointroduce a halide in a terminal position on the fluoropolymer.

[0038] Examples of chain transfer agents include those having theformula R_(f)Br_(x), wherein R_(f) is a x-valent (per)fluoroalkylradical C₁-C₁₂, optionally containing chlorine atoms, while x is 1 or 2.Examples include CF₂Br₂, Br(CF₂)₂Br, Br(CF₂)₄Br, CF₂ClBr, CF₃CFBrCF₂Br,and the like. Further examples of suitable chain transfer agents aredisclosed in U.S. Pat. No. 4,000,356, EP 407 937, EP 101 930 and U.S.Pat. No. 4,243,770.

[0039] Suitable organic peroxides are those which generate free radicalsat curing temperatures. A dialkyl peroxide or a bis(dialkyl peroxide)which decomposes at a temperature above 50° C. is especially preferred.In many cases it is preferred to use a di-tertiarybutyl peroxide havinga tertiary carbon atom attached to peroxy oxygen. Among the most usefulperoxides of this type are2,5-dimethyl-2,5-di(tertiarybutylperoxy)hexyne-3 and2,5-dimethyl-2,5-di(tertiarybutylperoxy)hexane. Other peroxides can beselected from such compounds as dicumyl peroxide, dibenzoyl peroxide,tertiarybutyl perbenzoate, α,α′-bis(t-butylperoxy-diisopropylbenzene),and di[1,3-dimethyl-3-(t-butylperoxy)-butyl]carbonate. Generally, about1-3 parts of peroxide per 100 parts of fluoropolymer is used.

[0040] Another component which is usually included in a cure compositionbased on an organic peroxide, is a coagent composed of a polyunsaturatedcompound which is capable of cooperating with the peroxide to provide auseful cure. These coagents can be added in an amount equal to 0.1 and10 parts per hundred parts fluoropolymer, preferably between 2-5 partsper hundred parts fluoropolymer. Examples of useful coagents includetriallyl cyanurate; triallyl isocyanurate; triallyl trimellitate;tri(methylallyl)isocyanurate; tris(diallylamine)-s-triazine; triallylphosphite; N,N-diallyl acrylamide; hexaallyl phosphoramide;N,N,N′,N′-tetraalkyl tetraphthalamide; N,N,N′,N′-tetraallyl inalonamide;trivinyl isocyanurate; 2,4,6-trivinyl methyltrisiloxane;N,N′-m-phenylenebismaleimide; diallyl-phthalate andtri(5-norbornene-2-methylene)cyanurate. Particularly useful is triallylisocyanurate. Other useful coagents include the bis-olefins disclosed inEPA 0 661 304 A1, EPA 0 784 064 A1 and EPA 0 769 521 A1.

[0041] In addition to the hydrotalcite compound, the fluoroelastomerlayer may further contain acid acceptors as are commonly used influoroelastomer layers. Such acid acceptors can be inorganic or blendsof inorganic and organic acid acceptors. Examples of inorganic acceptorsinclude magnesium oxide, lead oxide, calcium oxide, calcium hydroxide,dibasic lead phosphate, zinc oxide, barium carbonate, strontiumhydroxide, calcium carbonate, etc. Organic acceptors include epoxies,sodium stearate, and magnesium oxalate. The amount of acid acceptors inaddition to the hydrotalcite compound will generally depend on theamount of hydrotalcite compound used and the nature of the acid acceptorused. Typically, the amount of acid acceptor used should be such as tonot eliminate the advantage and improvements brought about by thehydrotalcite component of the composition. Generally, the amount of theacid acceptor will be less than the amount of hydrotalcite used and willtypically be less than 20% by weight relative to the weight ofhydrotalcite used. As hydrotalcite itself functions as an acid acceptor,the use of additional acid acceptor is generally not necessary and thusadditional acid acceptor may not need to be present in the composition.

[0042] The fluoropolymer composition for providing the fluoroelastomerlayer may contain further additives, such as carbon black, stabilizers,plasticizers, lubricants, fillers, and processing aids typicallyutilized in fluoropolymer compounding, provided they have adequatestability for the intended service conditions.

[0043] The fluoropolymer compositions may be prepared by mixing afluoropolymer, hydrotalcite, a cure composition and other additives inconventional rubber processing equipment. Such equipment includes rubbermills, internal mixers, such as Banbury mixers, and mixing extruders.

[0044] It is further possible to prepare a premix of the fluoropolymercomposition whereby the premix comprises the fluoropolymer and part ofother components of the full composition but not all of them. Thecomposition of such a premix will depend on desired stability of thepremix over a desired period of storage. For example, the premix maycomprise the fluoropolymer, the hydrotalcite and one or more componentsof a cure composition but not all of the components necessary to obtaina curable composition. For example, in case the cure compositioncomprises peroxide, it will generally be desired to exclude the peroxidefrom the premix and only add the peroxide at the time of preparing thefluoropolymer composition for preparing the fluoroelastomer layer.

[0045] In accordance with the method of the present invention for makinga component of a fuel management system, a curable fluoroelastomercomposition comprising a fluoropolymer preferably having one or morehalogens capable of participating in a cure reaction, an organicperoxide and a hydrotalcite compound is cured and shaped to form afluoroelastomer layer that in use will be in contact with fuel. Forexample, the fluoroelastomer layer having the hydrotalcite compound maybe an innermost layer of a fuel hose or a fuel tank. Typically, thehydrotalcite compound will be present in the fluoropolymer compositionand the fluoropolymer composition may also include a cure composition asdescribed above.

[0046] In one embodiment of the present invention for making a fuelmanagement system, a relatively thin layer of fluoroelastomer is formedas innermost layer of a multilayer hose or tank where the outer layer ofthe hose or tank is a non fluoropolymer. Examples of non fluoropolymersinclude non-fluorine type of elastomers, such as silicone rubbers,acrylonitrile butadiene rubber (NBR), butadiene rubber, chlorinated andchloro-sulfonated polyethylene rubber, chloroprene, copolymers ofethylene and propylene (EPM) rubber, terpolymer of ethylene, propylene,and a diene (EPDM) rubber, ethylene oxide and chloromethyl oxirane (ECO)rubber, epichlorohydrin-ethylene oxide-allylglycidylether terpolymer(GECO), polyisobutylene, polyisoprene, polysulfide, polyurethane, blendsof polyvinyl chloride and NBR, styrene butadiene (SBR) rubber,ethylene-acrylate copolymer rubber (VAMAC), and ethylene-vinyl acetaterubber and its hydrolysed form (EVOH) and thermoplastic elastomersderived from ethylene-propylene-diene terpolymer (EPDM), (EVOH) and apolypropylene. Bonding of the fluoropolymer layer to an elastomericlayer of a substrate may involve providing the fluoropolymer layer on alayer comprising a composition that upon curing forms the elastomericlayer. Particularly preferred outer layer can be formed from VAMAC orECO.

[0047] Further outer layers can be a metal substrate or a plasticsubstrate including for example a non-fluorinated polymer. Examples ofnon-fluorinated polymers include a polyamide, a polyolefin, apolyurethane, a polyester, a polyimide, a polystyrene, a polycarbonate,a polyketone, a polyurea, a polyacrylate, and a polymethylmethacrylate,or a mixture thereof. Polyamides useful as the non-fluorinated polymericsubstrate are generally commercially available. For example, polyamidessuch as any of the well-known nylons are available from a number ofsources. Particularly preferred polyamides are nylon-6, nylon-6,6,nylon-11, and nylon-12. It should be noted that the selection of aparticular polyamide material should be based upon the physicalrequirements of the particular application for the multi-layer article.For example, nylon-6 and nylon-6,6 offer better heat resistanceproperties than nylon-11 and nylon-12, whereas nylon-11 and nylon-12offer better chemical resistance properties. In addition, other nylonmaterials such as nylon-6,12, nylon-6,9, nylon-4, nylon-4,2, nylon-4,6,nylon-7, and nylon-8 can be used, as well as a polymer blend of nylon 6and polyolefin.

[0048] Useful polyolefin polymers include homopolymers of ethylene,propylene, and the like, as well as copolymers of these monomers with,for example, acrylic monomers and other ethylenically unsaturatedmonomers such as vinyl acetate and higher alpha-olefins. Such polymersand copolymers can be prepared by conventional free radicalpolymerization or catalysis of such ethylenically unsaturated monomers.The degree of crystallinity of the polymer can vary. The polymer may,for example, be a semi-crystalline high density polyethylene or can bean elastomeric copolymer of ethylene and propylene. Carboxyl, anhydride,or imide functionalities can be incorporated into the polymer bypolymerizing or copolymerizing functional monomers such as acrylic acidor maleic anhydride, or by modifying the polymer after polymerization,e.g., by grafting, by oxidation, or by forming ionomers. Examplesinclude acid modified ethylene acrylate copolymers, anhydride modifiedethylene vinyl acetate copolymers, anhydride modified polyethylenepolymers, and anhydride modified polypropylene polymers.

[0049] In another embodiment of the present invention for making a fuelmanagement system, a relatively thin layer of fluoroelastomer,comprising hydrotalcite, can be used as innermost layer of a multilayerhose or tank, a second layer is formed by using a thermoplasticfluoropolymer, in particular a melt processible thermoplasticfluoropolymer and the outer layer can be formed of a non fluorochemicallayer as decribed above. By the term “thermoplastic fluoropolymer” ismeant a fluoropolymer that is at least partially crystalline such that adistinct melting point, typically 100° C. or more, can be identified forexample through a DSC scan of the polymer. By the term “meltprocessible” is meant that the fluoropolymer has a melt viscosity suchthat it can be processed from the melt through typical melt extrusionequipment that is available. Preferably, the thermoplastic fluoropolymeris a fluoropolymer that is halogenated with one or more halogensselected from chlorine, bromine and iodine. Such halogen atoms may beintroduced in the fluoropolymer by copolymerization of a bromine oriodine containing comonomer, e.g. as listed above, or through the use ofchain transfer agents and/or initiator systems that introduce Br or Iatoms. Specific examples of thermoplastic fluoropolymers that may beused with this invention are copolymers having the following combinationof monomers: CTFE-VDF; CTFE-TFE, CTFE-TFE-HFP, CTFE-TFE-HFP-VDF;CTFE-TFE-HFP-VDF-PPVE, CTFE-TFE-E; bromine or chlorine containing E-TFEcopolymers and bromine or chlorine containing TFE-HFP-VDF copolymers.

[0050] Fuel management systems based on multiple layers such as amulti-layer hose having a fluoroelastomer layer bonded to athermoplastic fluorochemical and/or non fluoropolymer can be produced byany of the known methods for making multi-layer articles. For example,each of the layers can be co-extruded to form a multi-layer hose.Bonding of the fluoroelastomer inner layer to the intermediatethermoplastic fluorochemical and/or the non fluorochemical outer layermay be affected by applying heat to a temperature of 120° C. to 200° C.and for 1 to 120 min (preferably 140° C. to 180° C. and for 3 to 60min). The heating may further be carried out while simultaneouslyapplying pressure. It may, however, be desirable to further treat theresulting article, e.g.hose, for example, with additional heat,pressure, or both, to enhance the bond strength between the layers. Oneway of supplying additional heat when the multi-layer article isprepared by extrusion is by delaying the cooling of the multi-layerarticle at the conclusion of the extrusion process. Alternatively,additional heat energy can be added to the multi-layer hose bylaminating or extruding the layers at a temperature higher thannecessary for merely processing the components. For example, thefinished article can be placed in a separate apparatus for elevating thetemperature of the article such as an oven or autoclave. Combinations ofthese methods can also be used. The particular method or methods usedwill generally depend on the component of the fuel management systemthat is being produced.

[0051] In order to improve the bonding between the separate layers, acompound having one or more groups capable of participating in a freeradical reaction, such as ethylenically unsaturated groups, may be used.The compound having such groups may be present in the non-fluorochemicallayer and/or the fluoropolymer layers. For example, a compound havingunsaturated groups may be the coagent of a peroxide cure compositiondescribed above. Generally, reacting the fluoropolymer layer to the nonfluorochemical layer will also involve the use of a free radicalgenerating compound such as for example a free radical polymerizationinitiator. Preferably, an organic peroxide is used as a free radicalgenerating compound in particular if the fluoropolymer layer includes aperoxide cure system as a cure composition. However, also other freeradical generating compounds can be used such as for example azocompounds.

[0052] Several layer arrangements of the fuel management system can becontemplated and used. For example, the fluorochemical elastomer layer,comprising hydrotalcite, may be provided as an innermost layer in abilayer construction with a non fluorochemical polymer as outmost layer.Alternatively, a multilayer arrangement can be used in which athermoplastic fluoropolymer is provided between two layers. For example,a fluoroelastomer layer, comprising hydrotalcite, can be used as aninnermost and the outermost layer can be a non-fluorinated polymer layerincluding a non-fluorine type of elastomer.

[0053] According to one embodiment, a hose for use in a fuel managementsystem can be made in which a layer of fluoroelastomer, comprisinghydrotalcite, as an innermost layer, is bonded to a non-fluorinepolymer, in particular an ethylene-acrylate copolymer rubber.

[0054] According to a further embodiment, a hose for use in a fuelmanagement system can be made in which a fluoroelastomer layer,comprising hydrotalcite, as an innermost layer, is bonded to athermoplastic fluorochemical as intermediate layer, that is bonded to anon-fluorine polymer, in particular an ethylene-acrylate copolymer or asilicone copolymer.

[0055] According to a further embodiment, a hose for use in a fuelmanagement system can be made in which a fluoroelastomer layer,comprising hydrotalcite, as an innermost layer, is bonded to anon-fluorine polymer, such as ethylene vinyl acetate and its hydrolysedform (EVOH) as intermediate layer, that is bonded to a non-fluorinepolymer, in particular an ethylene-acrylate copolymer or a siliconecopolymer.

[0056]FIG. 1 and FIG. 2 further illustrate a component of a fuelmanagement system according to this invention in the form of a tube orhose, for example, a hose suitable for use as a fuel line in anautomobile system. Referring to FIG. 1, there is shown a two-layerarticle 10 that includes a relatively thick outer layer 18 bonded to aninner layer 14. Outer layer 16 is the non-fluorinated polymer layer, asdescribed above, and is designed to provide article 10 with structuralintegrity.

[0057] Outer layer 16 forms outer surface 18 of the hose. Thenon-fluorinated polymer can include an elastomer (e.g., silicone rubber,ethylene-acrylic rubber, and the like) and a plastic (e.g., polyamide).Inner layer 14 is the fluoroelastomer, comprising hydrotalcite. Innerlayer 14 forms inner surface 12 of the hose. Inner layer 14 impartschemical and thermal stability to the hose. Inner layer 14 also servesas a barrier or protective layer for outer layer 16 protecting it fromfuel. Some or all of the layers can include an additive to render themelectrically conductive. To further enhance structural integrity,reinforcing aids such as fibers, mesh, braid, and/or a wire screen canbe incorporated in article 10, e.g., as separate layers or as part of anexisting layer.

[0058] Referring to FIG. 2, there is shown a three-layer article 20 thatincludes a relatively thick outer layer 28 bonded to an intermediatelayer 26, which is bonded to a thinner inner layer 24. Outer layer 28can be the non-fluorinated polymer layer, as described above, and isdesigned to provide article 20 with structural integrity. Outer layer 28forms outer surface 30 of the hose. The non-fluorinated polymer caninclude an elastomer (e.g., ethylene-acrylate copolymer, siliconecopolymer, nitrile rubber, epichlorohydrin rubber, and the like), whichcan improve the sealing properties of the article when the hose or tubeis attached to a rigid connector. Inner layer 24 is a fluoroelastomer,comprising hydrotalcite. Inner layer 24 forms inner surface 22 of thehose. Inner layer 24 imparts chemical and thermal stability to the hose.Because of solvent and permeation resistance of the fluoroelastomer,comprising hydrotalcite, inner layer 24 improves the sealing propertiespreventing leaking at the ends. Intermediate layer 26 can be athermoplastic fluoropolymer layer, which can add to the barrierproperties of the inner layer. The combination of inner layer 24 andintermediate layer 26 minimizes the total amount of permeation from thehose and connections within a system. Some or all of the layers caninclude an additive to render them electrically conductive. To furtherenhance structural integrity, reinforcing aids such as fibers, mesh,braid, and/or a wire screen can be incorporated in article 20, e.g., asseparate layers or as part of an existing layer. For example, not shownin the drawing, a reinforcement layer can be included in the compositionbetween outer layer 28 and intermediate layer 26.

[0059] The invention will now be described with reference to thefollowing examples without however the intention to limit the inventionthereto. All parts are by weight unless indicated otherwise.

EXAMPLES

[0060] All parts and percentages are by weight unless stated otherwise

Abbreviations

[0061] Ca(OH)₂: calcium hydroxide, Rhenofit CF, Rhein Chemie.

[0062] Trigonox™ 101 45B: organic peroxide, AKZO

[0063] Perkalink™ 301-50D: triallyl-isocyanurate, 50% on silicatecarrier, Akzo

[0064] DIAK™ no. 8: trimethallyl-isocyanurate, available from NipponKasei

[0065] FE-1: fluoropolymer of tetrafluoroethylene, vinylidene fluorideand hexafluoropropylene and further including bromotrifluoroethylene asa cure site monomer

[0066] FE-2: fluoropolymer having cure sites, GF 300™, available fromDupont de Nemours

[0067] MT N-990: carbon black, available from Cancarb.

[0068] Biodiesel: diesel comprising RME (rape seed oil methyl ester,available from Globus, Germany

[0069] DHT-4V™: hydrotalcite, available from Kisuma Chemicals BV andcorresponding to the formula Mg_(4.5)Al₂(OH)₁₃CO₃3.5H₂O

[0070] Test methods

[0071] Cure and Theological properties of fluoroelastomer compositionswere evaluated using the following test methods:

[0072] Physical property testing was obtained after 150 by 150 by 2 mmsheets were pressed and allowed to vulcanise for 15 minutes at 180° C.mold temperature followed by post-curing treatment by heating the sheetsin a circulating air oven maintained at about 180° C. for 2 hours.Tensile Strength at Break, Elongation at Break and Stress at 100%Elongation were determined using an Instron™ mechanical tester with a 1kN load cell in accordance with DIN 53504 (S2 die). Test specimen strips(dumbbell) were cut from post-cured sheets. All tests were run at aconstant cross head displacement rate of 200 mm/min in fivefold. Thevalues reported were averages of the five tests. Hardness Shore A (2″),Stress at 100% Elongation, Elongation at Break, and Tensile Strength atBreak were reported in units of Mega Pascals (MPa), %, and MParespectively.

Examples Examples 1 to 3 and Comparative Examples C-1 to C-3

[0073] In examples 1 to 3 and comparative examples C-1 to C-3, curablecompositions were made on a two-roll mill by mixing compounds as givenin table 1. The compounds are presented in parts by weight per hundredparts by weight of fluoroelastomer (phr) as is custom in the rubberindustry. Examples 1 to 3 contained hydrotalcite at a level as given intable 1, comparative examples C-1 to C-3 were made without the additionof hydrotalcite. Comparative example C-1 and C-3 contained 3 phr Ca(OH)₂and comparative example C-2 contained 3 phr MgO as acid acceptors. Curedsamples were subjected to biodiesel with or without addition of waterand at a temperature and time as given in table 2. The volume swell isrecorded in table 2. The physical properties of the cured samples weremeasured before and after they had been immersed in biodiesel orbiodiesel +5% H₂O for Ex 2, at reflux in open system at 150° C., during504 hrs, followed by 22 hrs drying at 150° C. The results are given intable 3. TABLE 1 Composition of fluoroelastomer compounds Compound Ex 1Ex 2 C-1 C-2 Ex 3 C-3 FE-1 100 100 100 100 / / FE-2 / / / / 100 100 MTN-990 30 30 30 30 30 30 DHT-4V ™ 3 1 / / 3 / Ca(OH)₂ / / 3 / / 3 MgO / // 3 / / Trigonox ™ 101 45B 4.5 4.5 4.5 4.5 4.5 2.5 Diak ™ N° 8 1.5 2 2 21.5 / Perkalink ™ 301-50D / / / / / 5

[0074] TABLE 2 Volume swell after immersion in biodiesel Ex Volume swell(%) Solvent 1 Ex 2 C-1 C-2 Ex 3 C-3  96 hrs 150° C. biodiesel 3.3 2.516.1 3.5 2.4 4.6 288 hrs 150° C. biodiesel 2.9 3.1 38.4 4.3 3.3 9.2 504hrs 150° C. biodiesel 3.1 2.9 47.2 34.2 3.0 39 288 hrs 150° C.biodiesel + 2.4 5% H₂O

[0075] TABLE 3 Vulcanisate properties (press cured 15 min @ 180° C.,post cured 2 hrs @ 180° C.), after immersion in biodiesel Ex 1 Ex 2 C-1Ex 3 C-2 C-3 Hardness shore A (2″) 77 76 77 78 77 72 after immersiondifference to original 5 0 0 1 3 2 (points) Modulus 100% (Mpa) 5.9 6.27.6 8.2 4.4 5.4 % difference to original 4 13 12 34 7 15 Tensile (Mpa)18.0 17.0 6.3 15.5 18.2 12.3 % difference to original 10 6 −64 −13 0 −40Elongation (%) 185 181 84 155 232 183 % difference to original −2 −5 −54−19 −7 −27

[0076] The results in table 2 indicate that the addition of hydrotalciteto the fluoropolymer has a significant improvement on the swellingbehaviour of the fluoroelastomer in contact with biodiesel. Even anextended exposure to biodiesel at high temperature did not cause severeswelling.

1. Component of a fuel management system having a surface that in usewill come into contact with fuel, said surface comprising afluoroelastomer layer comprising a hydrotalcite compound dispersedtherein.
 2. Component according to claim 1 wherein said componentcomprises a fuel hose and said fluoroelastomer layer constitutes theinnermost layer of said fuel hose.
 3. Component according to claim 1wherein said component comprises a fuel tank and said fluoroelastomerlayer constitutes the innermost layer of said fuel tank.
 4. Componentaccording to claim 1 wherein said hydrotalcite compound is present in anamount of 0.3 to 20% by weight based on the fluoroelastomer. 5.Component according to claim 1 wherein said hydrotalcite compoundcomprises a synthetic hydrotalcite compound.
 6. Component according toclaim 1 wherein said hydrotalcite compound corresponds to the formula:[(M₁ ²⁺)_(a)(M₂ ²⁺)_(b)](M³⁺)_(y)(OH)_(2x+3y−2)(A^(n−))_(y/n)wH₂Owherein M₁ ²⁺ represents at least one divalent metal selected from thegroup consisting of Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺; M₂ ²⁺ represents at leastone divalent metal selected from the group consisting of Zn²⁺, Cd²⁺,Pb²⁺ and Sn²⁺; M³⁺ represents a trivalent metal ion; A^(n−) representsan n− valentanion; a and b each independently represents a value from 0to 10, x represents a+b and has a value from 1 to 10, y represents aninteger from 1 to 5, and w represents a real number.
 7. Componentaccording to claim 1 wherein said component is a multi-layer articlecomprising a layer of a non-fluorinated elastomer.
 8. Componentaccording to claim 1 wherein said fluoroelastomer layer comprises thecured product of a curable composition comprising (i) a fluoropolymerhaving a partially or fully fluorinated backbone and having a halogencapable of participating in a peroxide cure reaction and (ii) an organicperoxide.
 9. Component according to claim 8 wherein said fluoropolymeris a polymer comprising units deriving from tetrafluoroethylene and/orchlorotrifluoroethylene and one or more fluorinated monomers selectedfrom the group consisting of vinylidene fluoride, hexafluoropropyleneand a perfluorinated vinylether.
 10. A method comprising utilizing ahydrotalcite compound in a fluoroelastomer layer of a fuel managementcomponent to prevent or reduce swelling of said fluoroelastomer layerwhen said fluoroelastomer is contacted with a diesel fuel of biologicalorigin.
 11. Method of making a component of a fuel management systemcomprising: providing a curable fluoroelastomer composition including afluoropolymer having one or more halogens capable of participating in acure reaction, an organic peroxide and a hydrotalcite compound; andcuring and shaping said curable fluoroelastomer composition to form afluoroelastomer layer that in use will be in contact with fuel.